Thoughts on VoIP

Voice is not data, even in IP form. Voice is sensitive to jitter, delay and packet loss. Voice needs a network efficiency that data does not. QoS,CoS and RTP (see glossary) are often discussed in prioritizing the network traffic for optimum voice and video delivery. VLANs, switched ethernet and DiffServ as well as MPLS and Layer 4-7 switching can have a positive impact on QoS but may be limited to the LAN and MAN in your control.
"For toll quality phone calls, you need to shoot for a delay of less than 100ms. A large delay will cause the conversation to be ‘out of sync’. Delay is caused first by the length the VoIP data needs to travel, approximately 10ms of delay is introduced for every 1000 miles the data needs to travel."
- from QoS for Converged Voice/Data Networks by NetReality


Edgewater devices offer QoS built-in to the device to prioritize Voice traffic over data.
  • Replace hubs and 10 MB Switches with high-speed switches.
  • Increase memory on routers
  • Assess traffic patterns for congestion to determine if there is an upgrade need
  • Replace software-based processes or functions (e.g., firewalls) with hardware-based versions to reduce delay times and increase capacities.
  • Review of the network layout and architecture can be helpful.
- Jay R. Brandstadter of Delphi, Inc.

"Older VPN software wasn’t designed to handle the traffic that VoIP generates. Pushing voice through a VPN can, in some cases, degrade quality of service to the point of being unacceptable, experts say."

Voice is very important to clients - businesses and home users. If email goes down, a customer may be mad, but its not the same. (Plus email will keep trying delivery for 4 hours). If your voice service goes out,  it is not acceptable (or tolerated). Remember, the consumer has been spoiled by the five nines up-time of the PSTN. Talk to prospects about the likes and dislikes of their cell phone carrier to get an idea of what the expectations are.

When the power goes out, so does VoIP. This will be something new to the end user, who is used to POTS service. There is new CPE hitting the market may take care of this. Power over Ethernet (PoE) adapters are available from 3Com, Buffalo AirStation and others.
"Power outages pose a serious concern and may have an enormous cost to a business in terms of loss of productive output, loss of work-in-process, short sample of speech; beyond this level, packet loss will be very disruptive to voice communications." - Nortel white paper

  X11 Services to Consider:
- E911
- 411 (operator-assisted services)
- white/yellow page listings

NAT Transversal can be a headache. Those helpful little broadband routers now become an obstacle as your end user will have to set it up exactly as described in order to get the VoIP to work with NAT (on a self-install). MGCP has more difficulty with this than SIP, since there is middleware available for SIP to get through "pinholes" in NAT.

 Pinholes used for SIP can also be used for malicious attacks. This leads us to:
How do you secure it?

An IETF Working Group (MIDCOM) has been working on it for 2 years. Firewalls versus NAT. So far they have STUN

Simple Traversal of User Datagram Protocol (UDP) Through Network Address Translators (NATs) (STUN) is a lightweight protocol that allows applications to discover the presence and types of NATs and firewalls between them and the public Internet. It also provides the ability for applications to determine the public Internet Protocol (IP) addresses allocated to them by the NAT. STUN works with many existing NATs, and does not require any special behavior from them. As a result, it allows a wide variety of applications to work through existing NAT infrastructure.

But What About Packet Sniffing?

While it’s technically possible to sniff voice packets, it’s a lot more difficult than tapping into a traditional phone transmission. Let’s consider what it would take to tap into VoIP. The first step in sniffing a conversation is to gain physical access to the packets. This means having access to the switches and/or the corporate backbone network. But those same switches carry critical corporate data, which is far more sensitive than your conversations. If you’ve secured data against sniffing, you’ve secured voice. If you haven’t protected your data, voice packet sniffing isn’t your most serious security problem.

Of course, the transmission medium makes a difference.
Wireless Ethernet is far more susceptible to sniffing than copper wire. The most secure is fiber-optic cabling, which doesn’t emit radio frequencies as does copper wiring.
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“If you’re deploying a VoIP system, continually test and monitor it…to stay one step ahead of the potential bad guys who are out there.”  –JOEL POGAR, national practice manager for information security at Siemens


VoIP does not work very well with fax machines either. So that single line from the ILEC for 911 and 411 can be used for fax machines, DirectTV/DISH/TiVo dial-up, and security alarms. (Plus this single line will stay on when the power goes out.)

Note from BroadbandReports.com: "One user in our VoIP forum finds that by using a DSL filter in reverse orientation, their fax problems all but disappeared."

Can I plug my fax machine into my SPA-2000 for faxing?
Yes, you can fax over our network [Level(3)]. You can order a second dedicated line as a fax line or you can use a splitter. You need to set your fax to 9600 baud or lower.

Another work around is Fax2Email or efax. (I rep Fax2mail). Unified messaging platforms can handle the inbound fax-to-email and software such as WinFax can handle the electronic document to fax. But what to do about a piece of paper that  needs ink? Maybe an all-in-one printer connected to the network?

With Video Phones coming out, selling video conferencing should be easier as the CPE costs are dropping. The roll-out of 802.11 phones grants an opportunity to the NSP to create a wireless zone at an office and include VoIP and IP-PBX sales.

You could just get into the Calling Card game and sell cheap LD via VoIP.
Terminating Toll-Free & International Calls
If you are terminating VOIP calls (SIP, H.323, MGCP), RAD-INFO, Inc. (813.963.5884) has carriers that can provide this service for you.

Things I saved for next time: Echo, White Noise Generation, Traffic Engineering, IP-enabled Signalling and Directory Services, Codecs, Call Bandwidth, and Regulations (VoIP now must comply with CALEA).

RAD-INFO, Inc.
813.963.5884
NSP Strategist
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